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School me on tanks and canister lights

Discussion in 'Basic Scuba' started by TheCanuck, May 15, 2011.

  1. sam1

    sam1 Contributor

    # of Dives: 500 - 999
    Location: Jupiter, FL and Cape Cod, MA
    Interesting to see this comparison of tanks (i.e., cylinders!) with identical internal (liquid) volumes.

    If we add the weight of each tank to its buoyancy (when empty) we can compare the net weight differential between the two sets of tanks.

    LP108 vs. HP133: HP is 1.7 pounds heavier and 1.5 pounds less buoyant when empty for a net difference of +0.2 pounds---but you get 25 cubic feet more gas for carrying around +0.2 pounds more weight on your back/belt.

    LP120 vs. HP149: HP is 2.9 pounds heavier and 1.7 pounds less buoyant when empty for a net difference of +1.2 pounds---but you get 29 cubic feet more gas.
  2. ajduplessis

    ajduplessis Solo Diver

    # of Dives: I'm a Fish!
    Location: dry land :-(
    Please compare apples with apples!!! Internal volumes and materials (steel or ali, not both). The PST LP is 3" taller with a larger internal volume.

    With identical sized cylinders and the exact same liquid volume, LP will be lighter than HP.
  3. cbrich

    cbrich Solo Diver

    # of Dives:
    Location: Austin
    It does not surprise me that Faber has their s**t together, why not use the same hydraulic press to make 2 different cylinder, one cylinder made from 4340 steel (think 3AA cylinders are 4340) blank for LP cylinders, and another cylinder made from a special alloy blank to make HP133 cylinders.

    One of the things I find interesting, and maybe it's error on Faber's part for advertising the cylinders. But if you figure out cubic foot per psig, and then multiply by actual fill pressure; the numbers are skewed, and most people use this method to figure out volume needed on a planned deco dive. Also keep in mind the actual liquid volume for a 108 & 133 (the same goes for 120 & 149) are the same. A liquid (water) is uncompressable, so the volume does not change with pressure.

    LP108 vs. HP133 (simply calculated volume)
    (volume/rated pressure)*fill pressure = 108/2640*3442 = 140.8 cubic feet (assuming air compresses in a linear fashioin, an HP133 should really be HP140)

    LP120 vs. HP149
    120/2640*3442 = 156.5 cubic feet

    Both of these examples result in a 7.5 cubic feet of air being uncalcuated. I do remember from my college days, that air does not compress linear, but I don't remember the exact formula to figure that out.

    If anybody wants to send me a LP108 and HP133, I would be glad to cut them in half, length ways, and measure wall thickness, bottom thickness, and shoulder thickness. I expect the wall thickness to be the same since they use the same hydraulic press, but the bottom thickness will be different.
  4. kanonfodr

    kanonfodr Solo Diver

    # of Dives: 100 - 199
    Location: Seattle, Wa
    In addition to what others have stated, I would like to mention for the OP's sake that different tanks will trim differently in the water. HP120s tend to be very tail-heavy, HP80s are more head-heavy due to their lack of length. Cubic footage is nice, but it starts to get annoying when your bigger tanks are a pain to dive. If you are planning on purchasing tanks, keep that in mind.

  5. cbrich

    cbrich Solo Diver

    # of Dives:
    Location: Austin
    LED anyday of the week over Halogen. Halogen lights sucks a$$, even in homes, and as cars headlight. My preference is 1) HID, 2) LED, 3) don't dive at night.

    I personally own a Dive Rite 700LED, but wish I owned a 35 watt HID.
  6. TheCanuck

    TheCanuck Registered

    I already own two HP120s. I inherited them. I was wondering if it was worth it to use them as a set of doubles.

    How is it easier to fill mixed gases with a 3000psi cylinder versus a 3500 psi one?
  7. Doc Harry

    Doc Harry Solo Diver

    # of Dives: 500 - 999
    Location: Appalachia
    LED is the light of the future, not HID. If you want state of the art, go for LED.

    It is difficult (but not impossible) to get an LED light to focus tight enough for use in cave diving, but LED lights are in service in cave diing with pretty good reviews. However, most cave divers still seem to prefer HID at this time. Watch the trend change as the LED light head improves.

    If you're not using lights for cave diving, then I would get an LED with lithium (Li) or nickle-metal hydride (NiMH) batteries.

    Avoid acid gel batteries. Avoid Halogen lights. Old technology, poor performance.

    There are a lot of older 10W HID lights with NiMH batteries for sale for $300-$500. If you're looking for a nice light for night dives, I'd get one of these. ASk about the "burn time." Dunk the light in a big bucket of water and see how long the light burns on a fully charged battery.

    I prefer a can light with an indestructable battery connection, like the Halcyon lights. I had a Dive Rite HID that had the more typical electrical connectors, and had nothing but problems.

    Back in the year 402 B.C. Plato said, "A man cannot have too much wattage." I agree. Get the most powerful light that you can afford. Some people argue that you don't need or don't want a powerful light for night dives (scares away the animals). I disagree. The more light you have, the more things that you see.

    I dive in the caves of Mexico, where it is not possible to recharge the battery between dives. So I got the big battery pack that will last for numerous dives on one charge. If you're looking at just doing a night dive, then get a smaller, lighter battery pack that will get you through one night dive.

    Once you get a can light, you've got to be totally anal about mantaining the o-rings, or you WILL have a flooded light.
    TheCanuck likes this.
  8. markr

    markr Contributor

    # of Dives: 0 - 24
    Location: Maryland
    I did compare apples with apples. More precisely I compared tanks that hold similar volumes. If I want an 80cu.ft. tank the HP version is the lighter of the available options. Claiming that HP tanks are heavier because an HP133 weighs more then an LP108 is not comparing "apples to apples". I don't know how everybody else plans dives but I don't do it based on the length or diameter of the tank, I do it based on the volume of gas the tank holds, and for similar volumes of gas the high pressure tanks are lighter.
  9. cbrich

    cbrich Solo Diver

    # of Dives:
    Location: Austin
    My first question is, why do you want to double them up?

    At my LDS, the boosters cut off at 3,300 psig, eventhough they are capable of boosting up to 6,000 psig. This particular boost setup has a "safety pilot valve" (not for sure if this is the technical term) which limits the boosting pressure. So if they screw up on the amount of oxygen or helium in the mixture, they can not add anymore since the ending pressure is higher than 3,300. But that's not say the booster at your LDS is like that, they could have a simple booster setup.

    You are correct LEDs are the future, but for now they are only capable of meeting 10-15 watt HID, if you want a brighter light, then HID is the way to go. Halcyon, and Light Monkey make a 35 watt and 50 watt HID; it will be decades before a single LED diode will be on par with these high powered HID.

    They each have their pros and cons.

    Pro: compact, light weight, more energy efficent, and durable
    Cons: non-focusing beam (or at least I have not seen any), some have a wide beam (multi diodes), more expensive for single diode head vs. multi diode head.

    Pros: brighter, focusing beam, preferred by cave and wreck divers
    Cons: larger, bulbs are fragile, expensive for the 35 and 50 watt units

    I know the pros and cons list can go on and on, but selecting a light is up to you. You will be satisfied with either, LED or HID light. Light Monkey, Halcyon, and Dive Rite make very good units; there are other brands out there but I can not comment on them.
  10. cbrich

    cbrich Solo Diver

    # of Dives:
    Location: Austin
    You did make very good comparison, and I agree with you when comparing the same volume, but you can not please everyone because somebody will throw the high pressure fills in a LP cylinder, or the life expectancy of tank, or etc, etc. This comes down to how you compare the tanks.

    Just adding to your comparison of same volumes, but with Faber cylinders using the about the same volume, trying to hit 80 cubic foot.

    Rate Volume: 80 cubic foot
    Internal liquid Volume: 622 cubic inches
    Length: 20.87 inches (not including valve)
    Weight: 28.6 lbs (not including valve)
    Buoyancy: -8.05 to -1.74 lbs (not including valve)

    Rated Volume: 85 cubic foot
    Internal Liquid Volume: 793 cubic inches
    Length: 25.98 inches (the diameter of this tank is 7" not 7.25")
    Weight: 31.2 lbs
    Buoyancy: -3.8 lbs to 2.32 lbs

    LP80 (Faber does not specifically make an LP80 under the DOT specification cylinder, but they do have a 80 cubic foot cylinder rated at 2,640 psig under the exempt cylinder specification, FX100LPDVB)
    Rated Volume: 80 cubic foot
    Internal Liquid Volume: 787 cubic inches
    Length: 24.80 inches
    Weight: 24.9 lbs
    Buoyancy: 1.65 lbs to 7.65 lbs

    Luxfer AL80 (XS Scuba)
    Rated Volume: 77.4 cubic foot (I could not find the liquid volume of an AL80 tank)
    Length: 26.1 inches
    Weight: 31.4 lbs
    Bouyancy: -1.4 to 3.4 lbs

    When doing this comparison the HP80 is lighter, and smaller than the LP85 and the AL80s, but are also 6" shorter too. The height of the HP80s can and will affect the bouyancy and trim of a tall person. I can not dive HP80s because they put me in the head down position, and that is the worst position to be in. HP80s are good for some, but not so good for others.

    When doing this comparison, this is where almost everyone will pick the LP85s over the HP80s or the AL80s. I left out the LP80s under the exempt specifications because those cylinders float when full, who in their right mind would buy those cylinders? Why do you want to carry even more weight? I also left out the mid-pressure cylinders because those cylinders are bricks, -12.5 lbs (full) to -6.58 lbs (empty), again who in their right mind would buy those cylinders.

    My favorite cylinders are the HP100s. When I need to get larger cylinders, I will get HP133, because they are the HP version of the LP108.

    Rate Volume: 100 cubic foot
    Internal liquid Volume: 787 cubic inches
    Length: 25.39 inches (not including valve)
    Weight: 34.3 lbs (not including valve)
    Buoyancy: -8.41 to -0.59 lbs (not including valve)

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